Xref: utzoo comp.misc:2217 comp.periphs:859
Path: utzoo!mnetor!uunet!lll-winken!lll-tis!ames!mailrus!tut.cis.ohio-state.edu!bloom-beacon!mit-eddie!uw-beaver!uw-june!uw-entropy!dataio!pilchuck!ssc!markz
From: markz@ssc.UUCP (Mark Zenier)
Newsgroups: comp.misc,comp.periphs
Subject: Re: MFM encoding question
Message-ID: <1140@ssc.UUCP>
Date: 1 Apr 88 20:11:18 GMT
References: <752@ndsuvax.UUCP>
Organization: SSC, Inc., Seattle, WA
Lines: 23
Keywords: MFM
Summary: Its in your hardware

In article <752@ndsuvax.UUCP>, ncreed@ndsuvax.UUCP (Walter Reed) writes:
> I need information about how MFM data is encoded.  My computer writes
> directly to the disk (It's an amiga by the way) and MFM encoding has
> to be done.  Why do I need this info?  I am writing a conversion program
> for IBM format to amiga and back.  
> 

I assume you are talking about a floppy disk, in which case you need
the Intel or Nec databook with the 765 floppy disk chip in it.
(Actually the Western Digital 279x datasheets have more info.)

Unless the Amiga has a nonstandard disk controller, you only need to 
worry about the format. The number of sectors, tracks ,sector size.
The one catch is the inversion of the side select signal, which reverses
the location of the two tracks in a cylinder on a double sided disk.
(this is only a problem If you want to talk to some CPM machines like 
(I think) Kaypros).

You shouldn't care about the the encoding since the NEC/Intel controllers
and the western digital floppy controllers write the same sort of stuff.
It only matters if you are trying to deal with something wierd like 
Apple or Commodore 64 disks.  In that case your need one of the bit
oriented controllers like the ones Central Data or the people that
make uniform sell for the PC.